Late addition to effect compositional modifications in condensation polymers

ABSTRACT

A process for preparing modified polymer by withdrawing a slip stream of polymer melt from the discharge line of a continuous polymerization reactor, admixing in a highly modified polymeric additive into the polymer melt within the slip stream, then introducing the modifier containing slip stream late in the manufacturing process prior to the slip stream withdrawal point. The improved processes of the invention have particular utility for large-scale, continuous reactor where transitions and short production runs are economically prohibitive thereby limiting the product breath. The process is particularly suited for producing a family of copolyesters using a continuous melt phase production process.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser.No. 60/717,985, filed Sep. 16, 2005, the disclosure of which isincorporated herein by this reference.

FIELD OF THE INVENTION

The present invention relates to the preparation of a modified polymerby incorporating a compositional modifier into a slip stream of acontinuously discharged polymer melt stream to produce a modified slipstream followed by reintroduction of the modified slip stream into thepolymer melt prior to the slipstream withdrawal point. Moreparticularly, the invention relates the preparation of condensation typecopolyesters by withdrawing a slip stream of an unmodified- orslightly-modified polyester melt exiting a continuous polymerizationreactor, incorporating a highly-modified polymer into the slip stream,then reintroducing the modified slip stream into the continuouspolymerization reactor to produce a copolymer of intermediate comonomercontent.

BACKGROUND OF THE INVENTION

Condensation polymers such as thermoplastic polyesters, polycarbonates,and polyamides have many desirable physical and chemical attributes thatmake them useful for a wide variety of molded, fiber, and filmapplications. However, for specific applications, these polymers alsoexhibit limitations that must be minimized or eliminated. To overcomethese limitations, polymers are frequently made containing one or moreadditives or comonomers depending upon the desired end use of thepolymer. For example, in the case of polyester polymers, it is common toincorporate one or more ultra-violet absorbers, particles for improvingthe reheat of bottle preforms made from the polyester polymer, toners orpigments or colored particles, acetaldehyde scavengers or inhibitors,catalyst deactivators or stabilizers, oxygen barrier material, frictionreducing aids, crystallization aids, impact modifiers, and so forth.

One of the most common thermoplastic polyester polymers is polyethyleneterephthalate (PET). PET polymer is used extensively in the packagingindustry, especially in the production of bottles for carbonated andnon-carbonated beverages. In the carbonated beverage industry, concernsinclude the rate of carbon dioxide escape from the container, tastedeterioration of the contents due to degradation by light, andextraction of additives added either during melt polymerization orsubsequent melt processing required to fabricate the container. Toovercome these problems, PET resins are often modified by incorporatingunique comonomers into the polymer backbone thus producing a widevariety of PET copolyesters.

Several techniques have been employed to produce PET copolyesters. Inconventional polyester manufacturing, copolyesters are typicallyproduced by two different routes: ester exchange plus polycondensation(the DMT process) or direct esterification plus polycondensation (thedirect esterification process.) In the older ester exchange process, orDMT process, dimethyl terephthalate (DMT), ethylene glycol (EG), and themodifying comonomers are typically combined at the beginning of themanufacturing process in the paste tank or first esterification reactor;the modifying comonomer can be added as either a diacid, a dialkyl esterderivative of the acid, or a diol. In the presence of a catalyst atatmospheric pressure and at a temperature from about 180° C. to 230° C.,these components undergo ester interchange to yield the intermediatebis(hydroxyethyl ester) substituted monomer of the acids and methanol.

The reaction is reversible and is carried to completion by removing themethanol. After completion of the ester exchange, a stabilizer may thenbe added to deactivate the ester exchange catalyst and apolycondensation catalyst is then added. The intermediate monomers arethen polymerized by a polycondensation reaction, where the temperatureis raised to about 265° C. to about 305° C. and the pressure is reducedto below 2 mm of mercury vacuum in the presence of a suitablepolymerization catalyst (e.g. antimony). From this reaction,polyethylene terephthalate copolymer and ethylene glycol are formed.Because the reaction is reversible, the glycol is removed as it isevolved, thus forcing the reaction toward the formation of thepolyester.

The second method, or direct ester exchange process, is a well knownvariation of the DMT process and utilizes purified terephthalic acid(PTA) instead of DMT. In the first step, PTA is combined with ethyleneglycol (EG) and either diacids or diols of the modifying comonomers.Typically reacted without any catalyst and at a pressure from about 5psia to 85 psia and at a temperature from about 155° C. to 305° C.,these components undergo direct esterification to yieldbis(hydroxyalkyl) substituted intermediate monomers of the acids andwater. After the completion of the direct esterification, theintermediate monomers are then polymerized by the polycondensationreaction as described in the ester interchange process. That is, theintermediate monomers are then polymerized by raising the temperature toabout 265° C. to about 305° C. and the pressure is reduced to below 2 mmof mercury vacuum in the presence of a suitable polymerization catalyst(e.g. antimony). From this reaction, polyethylene terephthalatecopolymer and ethylene glycol are formed. Because the reaction isreversible, the glycol is removed as it is evolved, thus forcing thereaction toward the formation of the polyester.

With the increased availability of purified terephthalic acid, the newerdirect esterification offers many advantages including conversion from abatch process to a continuous process. Continuous processes are costeffective to operate when relatively large amounts of polyester orcopolymer are required. However, other problems occur relating to theuse of the continuous process to make copolyester when relatively smallamounts of copolyester are required and/or a family of copolyesters withvarying comonomer content is desired. In particular, a residence time onthe order of 4-to-12 hours is typical for a continuous polymerizationprocess; therefore, any changes in polymer compositions will generatesignificant amounts of off-class material. Problems associated withoff-class are further exacerbated at higher production rates on largerscale manufacturing lines making such equipment ill-suited forsmall-scale production of a diverse family of modified thermoplasticsresins containing varying compositions.

Several post-polymerization processes have also been utilized to producePET copolyesters. One approach has been to melt blend a PET base polymerwith a second, condensation type polymer using an extruder or reactionvessel, allowing the two polymers to undergo transesterification,thereby producing a random copolymer. This process exhibits severalshortcomings. First, extended reaction times up to ⅓ to two hours arerequired to achieve melt randomization thereby leading to thermaldegradation of the polymers and concurrent loss in physical properties,generation of color, and production of other undesirable degradationproducts such as acetaldehyde. Second, additional equipment either inthe form of large-scale, heated vessels or extruders are required toprovide the extended melt residence time. Third, additional catalystscan be incorporated to facilitate tranesterification thereby reducingthe melt residence time; however the additional catalysts willnegatively impact both the color and thermal stability of the resultanthomogenized copolymer. Lastly and most important, this process does notcapture the economic advantages associated with large-scale continuouslypolyester manufacturing processes.

Another post-polymerization process to prepare copolyesters comprisesmerging two reactor melt streams together wherein a melt stream ofhighly modified copolyester is feed into the discharge line ofcontinuously polymerized polyester of low or no modification andsubjecting the resins to static mixing and dynamic mixing in thedischarge line. A variant of this method involves withdrawing a sidesteam from the discharge line of the continuously produced PET baseresin, sending the side stream to an kneading extruder, introducing thehighly-modified copolyester into the kneading extruder, returning themodified side stream to the discharge line of the continuously producedPET base resin, then subjecting the resins to static mixing and dynamicmixing in the discharge line. Although the combination of static anddynamic mixing of these approaches likely improves the distributivemixing of these two components, it does not provide sufficient time toenable reactive randomization via transesterification of the twopolyesters. Furthermore, the addition of static and dynamic mixing unitsin the transport lines of a large-scale, continuous polymerization havethe disadvantage in that they require extensive cleaning between producttransitions, limiting their utility for agile production of a portfoliopolyester products.

In light of the above, there exists a need for a method to effect morerapid compositional changes during product transitions with generationof less off-class material in the production of copolyester resins bymelt phase polymerization, particularly in relation to large-scale,continuous plants designed to produce such polyesters. Thus, there is adesire to provide a method for adding a modifying polymer to a polymermelt stream in a manner which allows time for good mixing and chemicalequilibration.

BRIEF SUMMARY OF THE INVENTION

The present invention discloses a process for preparing a modifiedpolymer by:

-   -   a) discharging from a polymerization reactor a polycondensed        polymer melt to form a continuously discharged polymer melt        stream,    -   b) withdrawing a portion of the polymer melt from the        continuously discharged polymer melt stream to form a        slipstream,    -   c) introducing a compositional modifier into the slipstream to        form a modifier containing slipstream, and    -   d) introducing the modifier containing slipstream to a location        upstream from the point of withdrawing the polymer melt from the        discharged polymer melt stream in step b).

The improved processes of the invention have particular utility forlarge-scale, continuous reactor where transitions and short productionruns are economically prohibitive thereby limiting the product breath.The process is particularly suited for producing a family ofcopolyesters using a continuous melt phase production process. These andother aspects of the present invention will become apparent from thefollowing description.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the invention, as claimed. The accompanyingdrawings, which are incorporated in and constitute a part of thisspecification, illustrate several embodiments of the invention andtogether with the description, serve to explain the principles of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a process flow diagram illustrating a slipstream to which isfed a compositional modifier through an extruder.

FIG. 2 is a process flow diagram illustrating a slipstream to which isfed a compositional modifier through an in-line extruder

FIG. 3 is a process flow diagram illustrating a slipstream to which isfed a compositional modifier and another additive.

DETAILED DESCRIPTION OF THE INVENTION

The present invention may be understood more readily by reference to thefollowing detailed description and by reference to FIGS. 1-3 as anillustration of three embodiments, with other embodiments describedherein in further detail.

Before the present processes are disclosed and described, it is to beunderstood that this invention is not limited to specific syntheticmethods or to particular formulation, as such may, of course, vary. Itis also to be understood that the terminology used herein is for thepurpose of describing particular embodiments only and is not intended tobe limiting.

It must also be noted that, as used in the specification and theappended claims, the singular forms “a,” “an” and “the” include pluralreferents unless the context clearly dictates otherwise. For example,reference to processing or making a “polymer”, a “preform”, “article”,“container”, or “bottle” is intended to include the processing or makingof a plurality of polymers, preforms, articles, containers or bottles.References to a composition containing “an” ingredient or “a” polymer isintended to include other ingredients or other polymers, respectively,in addition to the one named.

By “comprising” or “containing” or “having” is meant that at least thenamed compound, element, particle, or method step etc. must be presentin the composition or article or method, but does not exclude thepresence of other compounds, catalysts, materials, particles, methodsteps, etc., even if the other such compounds, material, particles,method steps etc. have the same function as what is named, unlessexpressly excluded in the claims.

It is also to be understood that the mention of one or more method stepsdoes not preclude the presence of additional method steps before orafter the combined recited steps or intervening method steps betweenthose steps expressly identified. Moreover, the lettering of processsteps is a convenient means for identifying discrete activities orsteps, and unless otherwise specified, recited process steps can bearranged in any sequence.

Expressing a range includes all integers and fractions thereof withinthe range. Expressing a temperature or a temperature range in a process,or of a reaction mixture, or of a melt or applied to a melt, or of apolymer or applied to a polymer means in all cases that the limitationis satisfied if either the applied temperature, the actual temperatureof the melt or polymer, or both are at the specified temperature orwithin the specified range.

The word “composition” means that each listed ingredient is present inthe composition, and does not imply that any ingredient in thecomposition is unbound or unreacted. The composition may be solid orliquid. The stated ingredients in the composition may be bound, unbound,reacted, unreacted, and unless otherwise specified, in any oxidationstate.

The intrinsic viscosity (It.V.) values described throughout thisdescription are set forth in dL/g unit as calculated from the inherentviscosity (Ih.V.) measured at 25° C. in 60/40 wt/wtphenol/tetrachloroethane. Polymer samples are dissolved in the solventat a concentration of 0.25 g/50 mL. The viscosity of the polymersolution is determined using a Viscotek Modified DifferentialViscometer. A description of the operating principles of thedifferential viscometers can be found in ASTM D 5225. The inherentviscosity is calculated from the measured solution viscosity. Thefollowing equations describe these solution viscosity measurements, andsubsequent calculations to Ih.V. and from Ih.V. to It.V:η_(inh) =[ln(t _(s) /t _(o))]/C

-   -   where η_(inh)=Inherent viscosity at 25° C. at a polymer        concentration of 0.50 g/100 mL of 60% phenol and 40%        1,1,2,2-tetrachloroethane    -   ln=Natural logarithm    -   t_(s)=Sample flow time through a capillary tube    -   t_(o)=Solvent-blank flow time through a capillary tube    -   C=Concentration of polymer in grams per 100 mL of solvent        (0.50%)

The intrinsic viscosity is the limiting value at infinite dilution ofthe specific viscosity of a polymer. It is defined by the followingequation:η_(int) =lim _(C→0)(η_(sp) /C)=lim _(C→0) ln(η_(r) /C)

-   -   where η_(int)=Intrinsic viscosity    -   η_(r)=Relative viscosity=t_(s)/t_(o)    -   η_(sp)=Specific viscosity=η_(r)−1

Instrument calibration involves replicate testing of a standardreference material and then applying appropriate mathematical equationsto produce the “accepted” Ih.V. values.

Calibration Factor=Accepted Ih.V. of Reference Material/Average ofReplicate Determinations

Corrected Ih.V.=Calculated Ih.V.×Calibration Factor

The intrinsic viscosity (It.V. or η_(int)) may be estimated using theBillmeyer equation as follows:η_(int)=0.5[e ^(0.5×Corrected Ih.V)−1]+(0.75×Corrected Ih.V.)

The reference for calculating intrinsic viscosity (Billmeyerrelationship) is J. Polymer Sci., 4, 83-86 (1949).

Alternatively, the It.V can be measured using the above solvents andconcentrations measured according to ASTM D 5225-98 using a differentialviscometer to measure IV.

In one embodiment of the present invention, a process is disclosed forpreparing a modified polymer by:

-   -   a) discharging from a polymerization reactor a polycondensed        polymer melt to form a continuously discharged polymer melt        stream,    -   b) withdrawing a portion of the polymer melt from the        continuously discharged polymer melt stream to form a        slipstream,    -   c) introducing a compositional modifier into the slipstream to        form a modifier containing slipstream, and    -   d) introducing the modifier containing slipstream to a location        upstream from the point of withdrawing the polymer melt from the        discharged polymer melt stream instep b).

In another embodiment of the present invention, a process is disclosedfor preparing a series of modified polymers with varying levels ofblockiness. By blockiness, it is meant that section of molecular chainscontaining consecutive monomers derived from the compositional modifierare incorporated into the polymer chains of the polycondensed polymermelt produced by the process of the continuous polymerization reactor toyield a block copolymer. Not being bound by any theory, the extent ofblockiness is believed to be controlled by the time duration thecompositional modifier interacts with the polycondensed polymer meltwhile exposed to a melt phase temperature. By selecting an appropriatepoint to introduce the modifier containing slipstream into thepolymerization process producing the polycondensed polymer melt, thetime duration at the melt phase temperatures can be adjusted.Particularly suited for the compositional modifier of the presentinvention are condensation type polymers as they are capable ofundergoing transesterification reactions with a polyester polycondensedpolymer melt during exposure to melt processing to form a block modifiedpolymer. Condensation type polymers useful as the compositional modifierin the present invention include polyesters, polycarbonates, andpolyamides. The extent of transesterification can be determined bynuclear magnetic resonance (NMR).

In yet another embodiment of the present invention, a process isdisclosed for preparing a series of modified polymers of varyingcomonomer compositions wherein the modified polymer is a randomcopolymer. By random copolymer is meant each polymer chain of themodified polymer contains monomers derived from both the compositionalmodifier and the polycondensed polymer melt produced by the continuouspolymerization reactor and further, it is meant these monomers arerandomly arranged in the modified polymer chain. Particularly suited forboth the compositional modifier and the polycondensed polymer melt arepolyester type condensation polymers as they readily undergotransesterification reactions during exposure to melt processingtemperature to form a random copolyester modified polymer.

The melt phase process is suitable for continuously polycondensing apolymer thereby providing a discharged polymer melt stream. Thepolycondensed polymer melt is in a liquid or molten state and issuitable for receiving an additive. Examples of such polycondensedpolymer melts are thermoplastic polymers, preferably polyesters.

A polycondensed polymer melt contains any unit-type of polyesterincluding but not limited to homopolyesters, copolyesters, andterpolyesters and is understood to mean a synthetic polymer prepared bythe reaction of one or more difunctional carboxylic acids with one ormore difunctional hydroxyl compounds. Typically the difunctionalcarboxylic acid can be a dicarboxylic acid and the difunctional hydroxylcompound can be a dihydric alcohol such as, for example, glycols anddiols. Alternatively, the difunctional carboxylic acid may be a hydroxycarboxylic acid such as, for example, p-hydroxybenzoic acid, and thedifunctional hydroxyl compound may be an aromatic nucleus bearing 2hydroxyl substituents such as, for example, hydroquinone. Thepolycondensed polyester polymer is desirably a random polymer such thatthe monomer units in the polymer chain are randomly arranged rather thanarranged in a block fashion.

Preferred polycondensed polyester polymers contain repeating alkylenearyl units, such as alkylene terephthalate or alkylene naphthalaterepeat units in the polymer chain. More specific examples of theserepeating units include ethylene terephthalate, ethylene naphthalate,and trimethylene terephthalate. More preferred are polyester polymerswhich comprise:

-   -   (i) a carboxylic acid component comprising at least 80 mole % of        the residues of terephthalic acid, derivates of terephthalic        acid, naphthalene-2,6-dicarboxylic acid, derivatives of        naphthalene-2,6-dicarboxylic acid, or mixtures thereof, and    -   (ii) a hydroxyl component comprising at least 80 mole % of the        residues of ethylene glycol and 0 to 20 mole percent of either        1,4-cyclohexanedimethanol units, diethylene glycol units,        2,2,4,4-tetramethyl-1,3-cyclobutanediol units, modifying glycol        units having 2 to 16 carbons, or mixtures thereof,        based on 100 mole percent of carboxylic acid component residues        and 100 mole percent of hydroxyl component residues in the        polyester polymer.

Typically, polycondensed polyester polymers such as polyethyleneterephthalate are made by reacting a diol such as ethylene glycol with adicarboxylic acid as the free acid or its C₁-C₄ dialkyl ester to producean ester monomer and/or oligomers, which are then polycondensed toproduce the polyester. More than one compound containing carboxylic acidgroup(s) or derivative(s) thereof can be reacted during the process. Allthe compounds that enter the process containing carboxylic acid group(s)or derivative(s) thereof that become part of said polyester productcomprise the “carboxylic acid component.” The mole % of all thecompounds containing carboxylic acid group(s) or derivative(s) thereofthat are in the product, sum to 100. The “residues” of compound(s)containing carboxylic acid group(s) or derivative(s) thereof that are inthe said polyester product refers to the portion of said compound(s)which remains in the said polyester product after said compound(s) iscondensed with a compound(s) containing hydroxyl group(s) and furtherpolycondensed to form polyester polymer chains of varying length.

More than one compound containing hydroxyl group(s) or derivativesthereof can become part of the polycondensed polyester polymer. All thecompounds that enter the process containing hydroxyl group(s) orderivatives thereof that become part of said polyester product(s)comprise the hydroxyl component. The mole % of all the compoundscontaining hydroxyl group(s) or derivatives thereof that become part ofsaid polyester product(s) sum to 100. The “residues” of hydroxylfunctional compound(s) or derivatives thereof that become part of saidpolyester product refers to the portion of said compound(s) whichremains in said polyester product after said compound(s) is condensedwith a compound(s) containing carboxylic acid group(s) or derivative(s)thereof and further polycondensed to form polyester polymer chains ofvarying length.

The mole % of the carboxylic acid residues and the hydroxyl residues inthe product(s) can be determined by proton NMR.

The reaction of the carboxylic acid component with the hydroxylcomponent during the preparation of the polycondensed polyester polymeris not restricted to the stated mole percentages since one may utilize alarge excess of the hydroxyl component if desired, e.g. on the order ofup to 200 mole % relative to the 100 mole % of carboxylic acid componentused. The polyester polymer made by the reaction will, however, containthe stated amounts of aromatic dicarboxylic acid residues and ethyleneglycol residues.

In addition to a diacid component of terephthalic acid, derivates ofterephthalic acid, naphthalene-2,6-dicarboxylic acid, derivatives ofnaphthalene-2,6-dicarboxylic acid, or mixtures thereof, the carboxylicacid component(s) of the present polycondensed polyester polymer mayinclude one or more additional carboxylic acid modifier components. Suchadditional carboxylic acid modifier components include mono-carboxylicacid compounds, dicarboxylic acid compounds, and compounds with a highernumber of carboxylic acid groups. Examples include aromatic dicarboxylicacids preferably having 8 to 14 carbon atoms, aliphatic dicarboxylicacids preferably having 4 to 12 carbon atoms, or cycloaliphaticdicarboxylic acids preferably having 8 to 12 carbon atoms. More specificexamples of modifier dicarboxylic acids useful as an acid component(s)are phthalic acid, isophthalic acid, naphthalene-2,6-dicarboxylic acid,cyclohexane-1,4-dicarboxylic acid, cyclohexanediacetic acid,diphenyl-4,4′-dicarboxylic acid, succinic acid, glutaric acid, adipicacid, azelaic acid, sebacic acid, and the like, with isophthalic acid,naphthalene-2,6-dicarboxylic acid, and cyclohexane-1,4-dicarboxylic acidbeing most preferable. It should be understood that use of thecorresponding acid anhydrides, esters, and acid chlorides of these acidsis included in the term “carboxylic acid”. It is also possible fortricarboxyl compound branching agents and compounds with a higher numberof carboxylic acid groups to modify the polycondensed polyester polymer,along with monocarboxylic acid chain terminators.

In addition to a hydroxyl component comprising ethylene glycol, thehydroxyl component of the present polycondensed polyester polymer mayinclude additional glycol modifier components. Such additional glycolmodifier components include mono-ols, diols, or compounds with a highernumber of hydroxyl groups. Examples of modifier hydroxyl compoundsinclude cycloaliphatic diols preferably having 6 to 20 carbon atomsand/or aliphatic diols preferably having 3 to 20 carbon atoms. Morespecific examples of such diols include diethylene glycol; triethyleneglycol; 1,4-cyclohexanedimethanol; propane-1,3-diol; butane-1,4-diol;pentane-1,5-diol; hexane-1,6-diol; 3-methylpentanediol-(2,4);2-methylpentanediol-(1,4); 2,2,4-trimethylpentane-diol-(1,3);2,5-ethylhexanediol-(1,3); 2,2-diethyl propane-diol-(1,3);hexanediol-(1,3); 1,4-di-(hydroxyethoxy)-benzene;2,2-bis-(4-hydroxycyclohexyl)-propane;2,4-dihydroxy-1,1,3,3-tetramethyl-cyclobutane;2,2-bis-(3-hydroxyethoxyphenyl)-propane; and2,2-bis-(4-hydroxypropoxyphenyl)-propane.

As carboxylic acid modifier residues, the polycondensed polyesterpolymer may contain isophthalic acid and naphthalane dicarboxylic acid

Carboxylic acid modifiers residues and glycol modifier residues can bothbe present in amounts of up to 20 mole %, or up to 10 mole %, or up to 5mole %, or up to 3 mole %, or up to 2 mole %, based on the total molesof their respective component in the polycondensed polyester polymer.Mono, tri and higher functional modifiers are preferably present inamounts of only up to about 8 mole %, or up to 4 mole %.

The term “residue”, as used herein, means any organic structureincorporated into a polymer through a polycondensation and/or anesterification reaction from the corresponding monomer. The term“repeating unit”, as used herein, means an organic structure having adicarboxylic acid residue and a diol residue bonded through acarbonyloxy group. Thus, for example, the dicarboxylic acid residues maybe derived from a dicarboxylic acid monomer or its associated acidhalides, esters, salts, anhydrides, or mixtures thereof. As used herein,therefore, the term “dicarboxylic acid” is intended to includedicarboxylic acids and any derivative of a dicarboxylic acid, includingits associated acid halides, esters, half-esters, salts, half-salts,anhydrides, mixed anhydrides, or mixtures thereof, useful in a reactionprocess with a diol to make polyester. As used herein, the term“terephthalic acid” is intended to include terephthalic acid itself andresidues thereof as well as any derivative of terephthalic acid,including its associated acid halides, esters, half-esters, salts,half-salts, anhydrides, mixed anhydrides, or mixtures thereof orresidues thereof useful in a reaction process with a diol to makepolyester.

The polycondensed polymer melt of the present invention may also includesuitable additives normally used in polymers. Such additives may beemployed in conventional amounts and may be added directly to thereaction forming the matrix polymer. Illustrative of such additivesknown in the art are colorants, pigments, carbon black, glass fibers,fillers, impact modifiers, antioxidants, stabilizers, flame retardants,reheat aids, crystallization aids, acetaldehyde reducing compounds,recycling release aids, plasticizers, nucleators, mold release agents,compatibilizers, processing aids and the like, or their combinations.These additives may be introduced into paste tank, the esterificationractor, the prepolymerization reactor, the finishing reactor, and at anypoint in between. In addition, the polycondensed polymer melt may alsocontain compositional modifier and additives previously introduced intothe polycondensation reactor via the modifier containing slipstream.

All of these additives and many others and their use are known in theart and do not require extensive discussion. Therefore, only a limitednumber will be referred to, it being understood that any of thesecompounds can be used in any combination so long as they do not hinderthe present invention from accomplishing its objects.

To the polycondensed polymer melt, either in a prepolymerizationreactor, the final polycondensation reactor, or at any point beforewithdrawing slipstream, a modifier containing slipstream is added. Themodifier containing slipstream contains a compositional modifier.

The “compositional modifiers” useful according to the present inventionare condensation type polymers, preferably polyamides, polycarbonates,and polyesters. One embodiment of this invention is a process tointroduce a polyamide compositional modifier into a polycondensedpolymer melt of PET, for example, to enhance the barrier performance ofthe PET. Another embodiment is a process to produce a modified polymerwherein a polycarbonate modifying polymer is admixed into theprocondensed polyester polymer to, for example, produce a modifiedpolyester with enhanced glass transition temperature (T_(g)) andcorresponding increased maximum use temperature. Still anotherembodiment is a process whereby a compositional modifier such as acopolyester comprising a high comonomer content is introduced into apolycondensed polyester polymer melt stream of PET homopolymer therebyproviding a modified polymer of intermediate comonomer content to eachof the individual polyester feeds.

By “compositional modifier” we mean a condensation polymer that containseither a greater or lesser mole percent of diacid resides other thanterephthalic acid residues as present in the continuously producedpolymer melt or that contains a greater or lesser mole percent ofhydroxyl residues other than EG residues as present in the continuouslyproduced polymer melt. In addition, the modifying polymer may contain amonomer residue not present in the polycondensed polymer melt stream.For example, a modified polymer comprising 6 mole percentcyclohexandimethanol (CHDM) residue may be produced by adding a PETcompositional modifier comprising greater than 6 mole percent CHDMresidue, or greater than 10 mole percent CHDM residue, or greater than25 mole percent CHDM, or greater than 50 mole percent CHDM, or greaterthan 75 mole percent CHDM, or up to 100 mole percent CHDM to apolycondensed polyester polymer melt comprising less than 6 mole percentCHDM glycol modifier residue. In another example, a modified polymercomprising CHDM residue may be produced by adding a PET compositionalmodifier comprising greater than 6 mole percent CHDM residue, or greaterthan 10 mole percent CHDM residue, or greater than 25 mole percent CHDM,or greater than 50 mole percent CHDM, or greater than 75 mole percentCHDM, or up to 100 mole percent CHDM to a polycondensed PET polymer meltstream comprising 2 mole percent CHDM glycol modifier residue. In yetanother example, a modified polymer comprising CHDM residue may beproduced by adding a PET compositional modifier comprising greater than6 mole percent CHDM residue, or greater than 10 mole percent CHDMresidue, or greater than 25 mole percent CHDM, or greater than 50 molepercent CHDM, or greater than 75 mole percent CHDM, or up to 100 molepercent CHDM to a polycondensed PET homopolymer polymer meltcomprisingneither dicarboxylic acid modifier or glycol modifier residues. In stillanother example, a modified polymer comprising isophthalic acid (IPA)residue may be produced by adding a PET compositional modifiercomprising greater than 6 mole percent IPA residue, or greater than 10mole percent IPA residue, or greater than 25 mole percent IPA, orgreater than 50 mole percent IPA, or greater than 75 mole percent IPA,or up to 100 mole percent IPA to a polycondensed unmodified-PET polymermelt stream comprising neither dicarboxylic acid modifier or glycolmodifier residues. In another example, a modified polymer comprising 6mole percent isophthalic acid (IPA) residue may be produced by adding aPET compositional modifier comprising greater than 6 mole percent IPAresidue, or greater than 10 mole percent IPA residue, or greater than 25mole percent IPA, or greater than 50 mole percent IPA, or greater than75 mole percent IPA, or up to 100 mole percent IPA to a polycondensedpolyester polymer melt comprising less than 6 mole percent IPA glycolmodifier residue. In another example, a modified polymer comprising 6mole percent naphthalic dicarboxylic acid (NDA) residue may be producedby adding a PET compositional modifier comprising greater than 6 molepercent NDA residue, or greater than 10 mole percent NDA residue, orgreater than 25 mole percent NDA, or greater than 50 mole percent NDA,or greater than 75 mole percent NDA, or up to 100 mole percent NDA to apolycondensed polyester polymer melt comprising less than 6 mole percentNDA. In another example, a modified polymer comprising2,4-dihydroxy-1,1,3,3-tetramethyl-cyclobutane (TMCB) residue may beproduced by adding a PET compositional modifier comprising greater than6 mole percent TMCB residue, or greater than 10 mole percent TMCBresidue, or greater than 25 mole percent TMCB, or greater than 50 molepercent TMCB, or greater than 75 mole percent TMCB, or up to 100 molepercent TMCB to a polycondensed polyester polymer melt. Likewise, amodified polymer comprising dicarboxylic acid modifier and glycolmodifier residues may be produced by adding a PET compositional modifiercomprising greater than 6 mole percent IPA residue, or greater than 10mole percent IPA residue, or greater than 25 mole percent IPA, orgreater than 50 mole percent IPA, or greater than 75 mole percent IPA,or up to 100 mole percent IPA to a polycondensed polyester polymer meltcomprising greater than 1 mole percent CHDM residue, or greater than 10mole percent CHDM residue, or greater than 25 mole percent CHDM, orgreater than 50 mole percent CHDM, or greater than 75 mole percent CHDM,or up to 100 mole percent CHDM. Likewise, the dicarboxylic acid modifierand glycol modifier residues of the modified polymer may be reducedrelative to the polycondensed polyester polymer, this reduction beingachieved by adding a compositional modifier containing less dicarboxylicacid modifier and glycol modifier residues than the polycondensedpolyester polymer to which the compositional modifier is introduced. Anexample of such a dicarboxylic acid modifier and glycol modifierreduction is a modified polymer comprising less than 6 mole percentisophthalic acid (IPA) residue may be produced by adding a PETcompositional modifier comprising less than 6 mole percent IPA residue,or less than 4 mole percent IPA residue, or less than 2 mole percentIPA, or 0 mole percent IPA to a polycondensed polyester polymer meltcomprising 6 or greater mole percent IPA glycol modifier residue. Theseexamples are exemplary and are not restrictive of the invention, asclaimed and are intended to demonstrate the utility of the presentinvention to prepare a family of copolymers comprising a variety ofcomonomer residues in varying mole percent incorporation.

Suitable polyamide compositional modifiers include partially aromaticpolyamides, aliphatic polyamides, wholly aromatic polyamides andmixtures and copolymers thereof which are derived from diamines anddicarboxylic acids and/or from aminocarboxylic acids or theircorresponding lactams. By “partially aromatic polyamide” it is meantthat the amide linkage of the partially aromatic polyamide contains atleast one aromatic ring and a nonaromatic species.

The polyamides are generally prepared by processes which are well knownin the art. A typical procedure is by melt phase polymerization from adiacid-diamine complex which may be prepared either in situ or in aseparate step. In either method, the diacid and diamine are used asstarting materials. Alternatively, an ester form of the diacid may beused, preferably the dimethyl ester. If the ester is used, the reactionmust be carried out at a relatively low temperature, generally 80° C. to120° C., until the ester is converted to an amide. The mixture is thenheated to the polymerization temperature.

Suitable polyamides have a film forming molecular weight and preferablyan I.V. of about 0.25 to about 1.5 dL/g, preferably about 0.4 to about1.2 dL/g, and more preferably of about 0.7 to about 0.9 dL/g. The I.V.is measured at 25° C. in a 60/40 by weight mixture inphenol/1,1,2,2-tetrachloroethane at a concentration of 0.5 grams per 100ml. Wholly aromatic polyamides comprise in the molecule chain at least70 mole % of structural units derived from m-xylene diamine or a xylenediamine mixture comprising m-xylene diamine and up to 30% of p-xylenediamine and an .alpha.epsilon.-aliphatic dicarboxylic acid having 6 to10 carbon atoms, which are further described in Japanese PatentPublications No. 1156/75, No. 5751175, No. 5735/75 and No. 10196/75 andJapanese Patent Application Laid-Open Specification No. 29697/75, thedisclosure of which is incorporated herein by reference.

Polyamides formed from isophthalic acid, terephthalic acid,cyclohexanedicarboxylic acid, meta- or para-xylene diamine, 1,3- or1,4-cyclohexanebis)methylamine, aliphatic diacids with 6 to 12 carbonatoms, aliphatic amino acids or lactams with 6 to 12 carbon atoms,aliphatic diamines with 4 to 12 carbon atoms, and other generally knownpolyamide forming diacids and diamines can be used. The low molecularweight polyamides may also contain small amounts of trifunctional ortetrafunctional comonomers such as trimellitic anhydride, pyromelliticdianhydride, or other polyamide forming polyacids and polyamines knownin the art.

Partially aromatic polyamides include: poly(m-xylylene adipamide),poly(m-xylylene adipamide-co-isophthalamide), poly(hexamethyleneisophthalamide), poly(hexamethylene isophthalamide-co-terephthalamide),poly(hexamethylene adipamideco-isophthalamide), poly(hexamethyleneadipamide-co-terephthalamide), poly(hexamethyleneisophthalamide-co-terephthalamide) and the like or mixtures thereof.More preferred partially aromatic polyamides include, but are notlimited to poly(m-xylylene adipamide), poly(hexamethyleneisophthalamide-co-terephthalamide), poly(m-xylyleneadipamide-co-isophthalamide), and mixtures thereof.

Suitable aliphatic polyamides include polycapramide (nylon 6),poly-aminoheptanoic acid (nylon 7), poly-aminonanoic acid (nylon 9),polyundecane-amide (nylon 11), polylaurylactam (nylon 12),polyethylene-adipamide (nylon 2,6), polytetramethylene-adipamide (nylon4,6), polytetramethylene-adipamide (nylon 6,6),polyhexamethylene-sebacamide (nylon 6,10), polyhexamethylene-dodecamide(nylon 6,12), polyoctamethylene-adipamide (nylon 8,6),polydecamethylene-adipamide (nylon 10,6), polydecamethylene-adipamide(nylon 12,6) and polyhexamethylene-sebacamide (nylon 12,8).

Suitable polycarbonate compositional modifiers include the condensationproduct of a carbonate source and a diol source having a carbonatecomponent containing 100 mole percent carbonate units and a diolcomponent containing 100 mole percent diol units, for a total of 200mole percent monomeric units. The term “diol” as used herein includesboth aliphatic and aromatic compounds having two hydroxyl groups.

The polycarbonates may be prepared by a variety of conventional and wellknown processes which include transesterification, melt polymerization,and interfacial polymerization. The polycarbonates are generallyprepared by reacting a dihydric phenol with a carbonate precursor, suchas phosgene, a haloformate or carbonate ester in melt or solution.Suitable processes for preparing the polycarbonates of the presentinvention are described in U.S. Pat. Nos., 2,991,273; 2,999,846;3,028,365; 3,153,008; 4,123,436; all of which are incorporated herein byreference.

The dihydric phenols employed are known, and the reactive groups arethought to be the phenolic hydroxyl groups. Typical of some of thedihydric phenols employed are bis-phenols such as2,2-bis-(4-hydroxyphenyl)-propane (bisphenol A),3,3,5-trimethyl-1,1-bis(4-hydroxyphenyl)-cyclohexane,2,4-bis-(4-hydroxyphenyl)-2-methyl-butane,1,1-bis-(4-hydroxyphenyl)-cyclohexane,.alpha.,.alpha.′-bis-(4-hydroxyphenyl)-p-diisopropylbenzene,2,2-bis-(3-methyl-4-hydroxyphenyl)-propane,2,2-bis-(3-chloro-4-hydroxyphenyl)propane,bis-(3,5-dimethyl-4-hydroxyphenyl)-methane,2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)-propane,bis-(3,5-dimethyl-4-hydroxyphenyl)-sulfide,bis-(3,5-dimethyl-4-hydroxyphenyl)-sulfoxide,bis-(3,5-dimethyl-4-hydroxyphenyl)-sulfone, dihydroxy benzophenone,2,4-bis-(3,5-dimethyl-4-hydroxyphenyl)-cyclohexane,alpha.,.alpha.′-bis-(3,5-dimethyl-4-hydroxyphenyl)-p-diisopropylbenzeneand 4,4′-sulfonyl diphenol. Other dihydric phenols might includehydroquinone, resorcinol, bis-(hydroxyphenyl)-alkanes,bis-(hydroxyphenyl)ethers, bis-(hydroxyphenyl)-ketones,bis-(hydroxyphenyl)-sulfoxides, bis-(hydroxyphenyl)-sulfides,bis-(hydroxyphenyl)-sulfones, and.alpha.,.alpha.-bis-(hydroxyphenyl)diisopropylbenzenes, as well as theirnuclear-alkylated compounds. These and further suitable dihydric phenolsare described, for example, in U.S. Pat. Nos. 2,991,273; 2,999,835;2,999,846; 3,028,365; 3,148,172; 3,153,008; 3,271,367; 4,982,014;5,010,162 all incorporated herein by reference. The polycarbonates ofthe invention may entail in their structure, units derived from one ormore of the suitable bisphenols.

The carbonate precursors are typically a carbonyl halide, adiarylcarbonate, or a bishaloformate. The carbonyl halides include, forexample, carbonyl bromide, carbonyl chloride, and mixtures thereof. Thebishaloformates include the bishaloformates of dihydric phenols such asbischloroformates of 2,2-bis(4-hydroxyphenyl)-propane, hydroquinone, andthe like, or bishaloformates of glycol, and the like. While all of theabove carbonate precursors are useful, carbonyl chloride, also known asphosgene, and diphenyl carbonate are preferred.

The polycarbonates of this invention have a weight average molecularweight, as determined by gel permeation chromatography, of about 10,000to 200,000 g/mol, preferably 15,000 to 80,000 g/mol and their melt flowindex, per ASTM D-1238 at 300.degree. C is about 1 to 65 g/10 min,preferably about 2 to 30 g/10 min. The polycarbonates may be branched orunbranched. It is contemplated that the polycarbonate may have variousknown end groups. These resins are known and are readily available incommerce.

Suitable polyester compositional modifiers are those condensation typepolyesters that when introduced into the polycondensed polyester polymermeltwill either introduce one or more new monomer residues or willchange the mole percent of the diacid residues or the glycol residues ofthe polycondensed polyester polymer to yield a modified polymer ofintermediate comonomer content. The compositional modifier can be usedto either lower or raise the carboxylic acid modifier residues orglycol, modifiers residues in the polycondensed polyester polymer. Themonomer ratios in the modified polymer will depend on the relativecomonomer content of the compositional modifier and the ratio ofcompositional modifier added to the polycondensed polyester polymer. Thepolymerizations methods described above to produce the polycondensedpolyester polymer melt is also applicable to production of the polyestercompositional modifier.

The polyester compositional modifier of the invention comprisepolyesters that incorporate one or more of the carboxylic acid modifierresidues and glycol modifiers residues such that the sum of the totalmodifier residue comprising the polyester compositional modifier is atleast 0.1 mole %, or at least 1 mole %, or at least 5 mole %, or atleast 10 mole %, or at least 25 mole %, or at least 50 mole %, or atleast 75 mole %, or at least 100 mole %, up to about 125 mole %, or upto 150 mole %, or up to 200 mole % based on a total mole percent of 200mole %, comprised of 100 mole % acid residues and 100 mole % glycolresidues.

In addition to a diacid component of terephthalic acid, derivates ofterephthalic acid, naphthalene-2,6-dicarboxylic acid, derivatives ofnaphthalene-2,6-dicarboxylic acid, or mixtures thereof, the carboxylicacid component of the polyester compositional modifier may be preparedusing one or more additional carboxylic acid modifier components. Suchadditional carboxylic acid modifier components include mono-carboxylicacid compounds, dicarboxylic acid compounds, and compounds with a highernumber of carboxylic acid groups. Examples include aromatic dicarboxylicacids preferably having 8 to 14 carbon atoms, aliphatic dicarboxylicacids preferably having 4 to 12 carbon atoms, or cycloaliphaticdicarboxylic acids preferably having 8 to 12 carbon atoms. More specificexamples of modifier dicarboxylic acids useful as an acid component(s)are phthalic acid, isophthalic acid, naphthalene-2,6-dicarboxylic acid,cyclohexane-1,4-dicarboxylic acid, cyclohexanediacetic acid,diphenyl-4,4′-dicarboxylic acid, succinic acid, glutaric acid, adipicacid, azelaic acid, sebacic acid, and the like, with isophthalic acid,naphthalene-2,6-dicarboxylic acid, and cyclohexane-1,4-dicarboxylic acidbeing most preferable. It should be understood that use of thecorresponding acid anhydrides, esters, and acid chlorides of these acidsis included in the term “carboxylic acid”. It is also possible fortricarboxyl compound branching agents and compounds with a higher numberof carboxylic acid groups to modify the polyester, along withmonocarboxylic acid chain terminators.

In addition to a hydroxyl component comprising ethylene glycol, thehydroxyl component of the polyester compositional modifier may beprepared using one or more additional glycol modifier components. Suchadditional glycol components include mono-ols, diols, or compounds witha higher number of hydroxyl groups. Examples of modifier hydroxylcompounds include cycloaliphatic diols preferably having 6 to 20 carbonatoms and/or aliphatic diols preferably having 3 to 20 carbon atoms.More specific examples of such diols include diethylene glycol;triethylene glycol; 1,4-cyclohexanedimethanol; propane-1,3-diol;butane-1,4-diol; pentane-1,5-diol; hexane-1,6-diol;3-methylpentanediol-(2,4); 2-methylpentanediol-(1,4);2,2,4-trimethylpentane-diol-(1,3); 2,5-ethylhexanediol-(1,3);2,2-diethyl propane-diol-(1,3); hexanediol-(1,3);1,4-di-(hydroxyethoxy)-benzene; 2,2-bis-(4-hydroxycyclohexyl)-propane;2,2,4,4-tetramethyl-1,3-cyclobutanediol units;2,2-bis-(3-hydroxyethoxyphenyl)-propane; and2,2-bis-(4-hydroxypropoxyphenyl)-propane. As glycol modifier components,the polyester compositional modifier may preferably contain suchcomonomers as 1,4-cyclohexanedimethanol,2,2,4,4-tetramethyl-1,3-cyclobutanediol units, and diethylene glycol.

To ensure introduction of the compositional modifier does not adverselyaffect the physical properties of the polycondensed polyester polymer,the polyester compositional modifier of the invention should have in It.V. of at least 0.45, or at least 0.50, or at least 0.55, or at least0.60, or at least 0.65, or at least 0.70, as measured at 25° C. in asolvent consisting of 60 weight percent phenol and 40 weight percenttetrachloroethane.

The continuously discharged polymer melt stream may be supplied by anypolymerization reactor utilized in the melt phase process for makingpolymers provided that a polymer melt is present. For condensation typepolymers and polyesters in particular, the reactors are desirablypolycondensation reactors, and they fall under a variety of one or morenames, including a prepolymerization reactor, a prefinishing reactor, afirst stage reactor, a second stage reactor, or a finishing reactor ortheir equivalents. Polycondensation is typically continued in one ormore finishing vessels and generally, but not necessarily, ramped up tohigher temperatures than present in the prepolymerization zone, to avalue within a range of from 250° C. to 310° C., more generally from 270to 300° C., until the It.V. of the melt is increased to a final desiredIt.V. The final vessel, generally known in the industry as the “highpolymerizer,” “finisher,” or “polycondenser,” is also usually operatedat a pressure lower than used in the prepolymerization zone to furtherdrive off the diol and/or other byproducts and increase the molecularweight of the polymer melt. The pressure in the finishing zone may bewithin the range of about 0.1 to 20 mm Hg, or 0.1 to 10 mm Hg, or 0.1 to2 mm Hg. Although the finishing zone typically involves the same basicchemistry as the prepolymer zone, the fact that the size of themolecules, and thus the viscosity differs, means that the reactionconditions also differ. However, like the prepolymer reactor, each ofthe finishing vessel(s) is operated under vacuum or inert gas, and eachis typically but not necessarily mechanically agitated to facilitate theremoval of the diol and/or other byproducts. While reference has beenmade to a variety of operating conditions at certain discrete It V.values, differing process conditions may be implemented inside oroutside of the stated It.V. values, or the stated operating conditionsmay be applied at It.V. points in the melt other than as stated.Moreover, one may adjust the process conditions based on reaction timeinstead of measuring or predicting the It.V. of the melt. The process isalso not limited to the use of tank reactors in series or parallel or tothe use of different vessels for each zone. For example, the reactorsmay be one or more pipe reactors. Nor is it necessary to split thepolycondensation reaction into a prepolymer zone and a finishing zonebecause the polycondensation reaction can take place on a continuum ofslight variations in operating conditions over time in onepolycondensation reactor or in a multitude of reactors in series, eitherin a batch, semi-batch, or a continuous process.

The polyester melt should have an It.V. of at least 0.2 dL/g, or atleast 0.3 dL/g, or at least 0.4 dL/g, or at least 0.5 dL/g in thedischarged polymer melt stream. Preferably, the polymer melt isdischarged from the final reactor used in the melt phase process. Morepreferably, the polymer melt is discharged from the bottom or last stageof the final reactor in the melt phase process. As shown in FIG. 1,polycondensed polymer melt 101 is fed into a final finishing (or finalpolycondensation) reactor vessel 102 where polycondensation iscontinued, is discharged from the vessel as a continuously dischargedpolymer melt stream 104 through a gear pump 103 or other suitable motiveforce. In one embodiment, the polyester polymer in the continuouslydischarged polyester polymer melt stream has an It.V. of at least 0.60dL/g, or at least 0.68 dL/g, or at least 0.72 dL/g, or at least 0.74dL/g, or at least 0.76 dL/g.

After reaching the target It.V. in the final reactor, the continuouslydischarged polymer melt stream is withdrawn for the melt phase processas a modified polymer and ultimately solidified by any technique. Themethod for solidifying the modified polymer from the melt phase processis not limited. Any conventional hot pelletization or dicing method andapparatus can be used, including but not limited to dicing, strandpelletizing and strand (forced conveyance) pelletizing, pastillators,water ring pelletizers, hot face pelletizers, underwater pelletizers andcentrifuged pelletizers. For example, molten modified polymer from themay be directed through a die, or merely cut, or both directed through adie followed by cutting the molten modified polymer. A gear pump may beused as the motive force to drive the molten modified polymer throughthe die. Instead of using a gear pump, the molten modified polymer maybe fed into a single or twin screw extruder and extruded through a die,optionally at a temperature of 190° C. or more at the extruder nozzle.Once through the die, the modified polymer can be drawn into strands,contacted with a cool fluid, and chopped into pellets, or the polymercan be pelletized at the die head, optionally underwater. The modifiedpolymer is optionally filtered through filters 114 to removeparticulates over a designated size before being cut.

The modified polymer is processed to a desired form, such as amorphousparticles. The shape of the modified polymer particles is not limited,and can include regular or irregular shaped discrete particles withoutlimitation on their dimensions, including stars, spheres, spheroids,globoids, cylindrically shaped pellets, conventional pellets, pastilles,and any other shape.

The invention can be further understood by reference to FIG. 1-3 and thedescription, each serving to illustrate one of the many embodimentswithin the scope of the invention. Other embodiments within the scope ofthe invention can be designed by reference to the description withoutdeparting form the spirit of scope of the invention.

As illustrated in FIG. 1, in step a) a continuously discharged polymermelt stream 101 is continuously discharged from a polymerization reactor102 using a positive displacement pump 103 into discharge line 104. Instep b), a portion of the continuously discharged polymer melt stream iswithdrawn from the discharge line 104 and fed or diverted to formslipstream 105. The amount diverted can be regulated by a valve or othersuitable means known in to regulate flows. A slipstream ram valve 106 isdepicted to allow removal of a portion of the discharged polymer meltstream into the slipstream 105. If desired, one may employ an optionalpositive displacement pump for slipstream valve 106 to provide motiveforce driving the slipstream molten polymer back to the reactor or anyother reactor upstream of the reactor from which the discharged polymerwas taken.

In step c), a compositional modifier 107 is fed into the slipstream 105to form a modifier containing slipstream 109. For example, as depictedin FIG. 1, compositional modifier 107 is first introduced into extruder110, melted, and then fed into slipstream 105. Both single screw andtwin screw extruders are applicable to this invention. Optionally, agear pump 108 may be provided at the discharge of the extruder 110 tohelp regulate the compositional modifier throughput and to provide thenecessary pressure for returning the slip stream polymer composition tothe melt phase reactor. In another embodiment as depicted in FIG. 2,extruder 110 is configured in-line with slipstream 105 allowing thecompositional modifier to be melted and blended with the slipstreamwithin the high-mixing environment of the extruder; a twin screwextruder is preferable. The amount of compositional modifier used may beregulated by any loss-in-weight feeder commonly employed with twin screwextruders. In yet another embodiment of the invention, the compositionalmodifier 107 is fed directly, in a molten form, from secondpolymerization reactor to slipstream 105. The amount of modifyingpolymer used may be regulated by a regulator such as a ram valve, flowmeter, or positive displacement pump.

Optionally in step c), an additive 112 can be introduced directly intothe slipstream 105. In one embodiment, the additive 112 can beintroduced into extruder 111 with the modifying polymer. In anotherembodiment, the additive can first be melt blended with a carrier resinto form a masterbatch, the carrier resin being preferably polyester andmore preferably the composition of either the polycondensed polymer meltor the compositional modifier. In another embodiment as depicted in FIG.3, the additive 112 is introduced into the slipstream prior tointroduction of the modifying polymer. In yet another embodiment, theadditive is introduced into the slip stream after the compositionalmodifier is introduced. In still another embodiment, both an optionalliquid or solid additive composition can be fed into the slipstream at afirst addition point, and downstream of the first addition point, asecond additive composition can be fed into the line in a similarfashion; both additive addition points into the slip stream beingindependent of the addition point of the compositional modifier.Introduction point of the optional additive is dependent on a number offactors including thermal sensitivity of the additive, potentialchemistries that can occur in the melt between the additive and othercomponents in the melt, and desired level of mixing.

To facilitate introduction of the an additive directly into the slipstream, the additive injection nozzle (not depicted) should be of adesign to prevent plugging. For example, the injection nozzle may have anozzle portion which protrudes to the center line of the slipstreampipe. Preferably the exit of tip of the nozzle should protrude into theslipstream a distance of ⅓ the radius of the slip stream pipe into thehigh shear region of the slip steam flow. The opening in the tip of thenozzle is restricted to a diameter sufficiently small to prevent theslipstream molten polymer from entering the nozzle. The smallrestriction creates a pressure drop across the tip as the additivecomposition is injected into the slipstream molten polymer. When the ramvalve is closed, a piston extension is inserted into the nozzle andextends through the nozzle tip preventing polymer from entering thenozzle.

The additive can be a liquid additive or a solid additive. An example ofa liquid additive is a phosphorus based compound used to stabilize ordeactivate polycondensation catalysts present in the discharged polymermelt stream. An example of a solid additive may include metal powders ordispersions used as reheat additives or slip agents, or barrier orscavenging material which optionally can be melted before feeding.Preferably, any solid additive is either added either directly into theextruder used to melt and introduce the modifying polymer or is firstcompounded into a similar or same type of polymer as made in the reactorto form a concentrate, and this concentrate is fed in molten form to theslipstream. The additive feed rate into the slipstream will depend onthe desired concentration of the additive in the finished polymer meltstream 120 ready for solidification.

For example, a solid concentrate comprising an additive and a polyesterpolymer having an It.V. of at least 0.60 dL/g may be melted and pumpedinto the slipstream at a predefined rate corresponding the apredetermined concentration of additive in the discharged polymer meltstream. The feed rate will be determined by the concentration of theadditives in the concentrate, the desired concentration of the additivein the discharged polymer melt stream, and the flow rate of theslipstream. The means by which the solid additive composition can bemade and fed can very. For example, as mentioned above, pre-manufacturedsolid concentrate pellets containing a concentrated amount of additivemay be fed to a single screw extruder, melted, and metered into theslipstream. Alternatively, one may compound and feed the neat additiveinto the slipstream in one step by introducing the additive directlyinto extruder 111 used to incorporate the compositional modifier.

Examples of additives that can be incorporated into the dischargedpolymer melt stream include crystallization aids, impact modifiers,surface lubricants, denesting agents, antioxidants, ultraviolet lightabsorbing agents, metal deactivators, colorants, nucleating agents,acetaldehyde reducing compounds, reheat rate enhancing aids, stickybottle additives such as talc, and fillers, oxygen barrier materials andthe like.

In another embodiment, optional additive is post consumer recyclepolyester polymer (“PCR”). The PCR can be metered using a loss-in-weightfeeder simultaneously into the extruder used to melted and introduce themodifying polymer into the slipstream. In this way, and convenient meansis provided for both adding and blending or transesterifying PCR intovirgin polyester polymer. In one embodiment, the final polymercomposition contains at least 5 wt. % PCR, or at least 10 wt. % PCR, orat least 15 wt. % PCR. In another embodiment, scrap, waste, or regroundvirgin polyester polymer can be added into the slipstream such that thefinal polyester polymer composition also contains at least 0.5 wt. %, orat least 1 wt. %, or at least 5 wt. % of scrap, regrind, or wastepolymer or even off-specification polymer.

The slipstream flow rates may be regulated by the pressure created inthe continuously discharged polymer melt stream 104 by gear pump 103.Depicted in FIG. 1 is a pressure driven slipstream line 105. Theslipstream flow rate may be determined by the concentration of additivesused to feed the slipstream and the desired concentration of additivesin the discharged polymer melt stream. The slip stream flow rate canvary from 2% to 50%, or 5% to 25% of the continuously discharged polymermelt rate depending on what type of additives are being added and thedesired discharge melt stream additive concentration. In a pressuredriven slipstream flow rate, the flow rate of the slipstream 105 willself balance by increasing the flow rate of the slipstream toaccommodate pressure drops in the loop.

Alternatively, a flow meter installed in slipstream line 105 can be usedto measure and adjust slipstream control valve 106 to vary theslipstream flow rate. As another alternative, a positive displacementpump can be installed in the slipstream line 105 to set a fixed orconstant flow rate, optionally a pre-determined flow rate. Theslipstream gear pump can act as both a pressure let-down device whilecontrolling the flow rate. The control valve 106 need not be supplied ifa gear pump is used in the slipstream take off line.

After the compositional modifier and optional additive are added intothe slipstream, one may in some cases find it desirable to optionallyemploy a mixing device to obtain good mixing between the modifyingpolymer, optional additive, and the slipstream polymer melt, especiallybetween dramatically different viscosity fluids or between solids andliquids. An in-line mixer may be employed in a pipe, or baffles or weirsmay be employed, or as depicted in FIG. 1, a static mixer 112 may beemployed. The type of mixing device used in not limited.

At any point along the slip stream, heat can either be added or removedfrom the polymer melt in the slipstream. Examples where temperatureregulation is needed include the addition of thermally sensitiveoptional additives, to improve the mixing characteristics of themodifying polymer and optional additives with the polymer melt in theslipstream, and in cases where endothermic or exothermic reactions occurbetween the modifying polymer, optional additives, and polymer melt inthe slip stream.

In the event the additive used is corrosive, the metallurgy of thepiping, mixers, valves, and pumps may be a Hastelloy or titanium orother suitable corrosion resistant material. Alternatively, a corrosionresistant silver coating or liner may be employed to protect thecorrosion susceptible materials.

Once the compositional modifier and optional additives have been addedinto the slipstream line 105 to form a modifier containing slipstream,the modifier containing slipstream is fed in a step d) to a locationupstream from the feed location forming the slipstream. This wouldinclude feeding the modifier containing slipstream to line 104 prior tothe takeoff point of slipstream 105, to the entry of a gear pump 103, tothe reactor 102 from which the polycondensed polymer melt wasdischarged, or to a pipe or reactor upstream of the final reactor 102.As depicted in FIG. 1, the modifier containing slipstream is fed back tothe reactor 102 through a ram valve 113. Optionally, the modifiercontaining slipstream may have been well mixed through a mixer such as astatic mixer 112.

Desirably, the modifier containing slipstream is fed to the bottom ofthe reactor 102. In this way, the modifier containing slipstream isadded late in the process after substantial completion ofpolycondensation, which is when one or more of the following conditionsare satisfied or thereafter and before solidification of the polyestermelt:

-   -   a) the polyester melt reaches an It.V. of at least 0.50 dL/g or    -   b) vacuum applied to the polyester melt, if any, is released, or    -   c) if the polyester melt is present in a melt phase        polymerization process, adding the additive within a final        reactor for making the polyester polymer or between the final        reactor and the take off point for forming a slipstream, or    -   d) if the polyester melt is present in a melt phase        polymerization process, following at least 85% of the time for        polycondensing the polyester melt; or    -   e) the It.V. of the polyester melt is within ±0.05 dl/g of the        highest It.V. obtained prior to solidification; or    -   f) at a point within 20 minutes or less prior to solidifying the        polyester.

Beyond the take off point to the slipstream 105, the discharged modifiedpolymer is fed to a solidification device (not depicted) and optionallyfed through filters 114.

The process is a continuous recirculation loop such that in operation ina steady state, the slipstream polymer melt 105 will already containsome amount of compositional modifier and optional additive, withadditional amounts of compositional modifier and optional additiveinjected into the slipstream line to form an enriched modifiercontaining slipstream relative to the concentration of compositionalmodifier and optional additive in the slipstream prior to the additiveaddition point.

By the method of the invention, one may effect more rapid compositionalchanges during product transitions with generation of less off-classmaterial in the production of copolymers by melt phase polymerization,particularly in relation to large-scale, continuous plants designed toproduce such polyesters. Additionally, there is provided a method foradding a modifying polymer to a polyester polymer melt stream in amanner which allows time for good mixing and chemical equilibration. Themethod also allows for late addition of optional additives therebyminimizing thermal degradation of the additive, permitting and which arealso well mixed into the final polymer melt.

The polyester polymer compositions of the invention are particularlyuseful to make stretch blow molded bottles, extrusion blow moldedbottles, bottle preforms, fibers for carpet or apparel or stuffing,sheets, films, trays, cosmetic bottles and trays, or pharmaceuticalsbottles and trays.

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention. Moreover, all patents, patent applications (published andunpublished, foreign or domestic), literature references or otherpublication noted above are incorporated herein by reference for anydisclosure pertinent to the practice of this invention.

1. A process for preparing a modified polymer comprising: a) dischargingfrom a polymerization reactor a polycondensed polymer melt to form acontinuously discharged polymer melt stream, b) withdrawing a portion ofthe polymer melt from the continuously discharged polymer melt stream toform a slipstream, c) introducing a compositional modifier into theslipstream to form a modifier containing slipstream, and d) introducingthe modifier containing slipstream to a location upstream from the pointof withdrawing the polymer melt from the discharged polymer melt streamin step b).
 2. The process of claim 1 wherein the polycondensed polymermelt is a polyester or a copolyester.
 3. The process of claim 2 whereinthe polycondensed polymer melt is a polyester comprising: (i) acarboxylic acid component comprising at least 80 mole % of the residuesof terephthalic acid, derivates of terephthalic acid,naphthalene-2,6-dicarboxylic acid, derivatives ofnaphthalene-2,6-dicarboxylic acid, or mixtures thereof, and (ii) ahydroxyl component comprising at least 80 mole % of the residues ofethylene glycol and 0 to 20 mole percent of residues selected from1,4-cyclohexanedimethanol units, diethylene glycol units,2,2,4,4-tetramethyl-1,3-cyclobutanediol units, modifying glycol unitshaving 2 to 16 carbons, or mixtures thereof, based on 100 mole percentof carboxylic acid component residues and 100 mole percent of hydroxylcomponent residues in the polyester polymer; wherein the continuous flowof polymer melt has an inherent viscosity of 0.50 to 1.2 dL/g, measuredat 25° C. in a solvent consisting of 60 weight percent phenol and 40weight percent tetrachloroethane.
 4. The process of claim 3 comprising 0to 20 mole % dicarboxylic acid units selected from the group consistingof isophthalic acid units, phthalic acid, cyclohexane-1,4-dicarboxylicacid, cyclohexanediacetic acid, diphenyl-4,4′-dicarboxylic acid,succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid,and mixtures thereof.
 5. The process of claim 3 comprising 0 to 20 mole% dicarboxylic acid units selected from the group consisting ofisophthalic acid units.
 6. The process of claim 3 comprising greaterthan 0 to 20 mole % glycol residues selected from the group consistingof 1,4-cyclohexanedimethanol units, diethylene glycol units,2,2,4,4-tetramethyl-1,3-cyclobutanediol units, and mixtures thereof. 7.The process of claim 3 wherein the polymer melt stream is a polyestercomprising an additive, said additive comprising a UV absorber, reheatrate enhancer, oxygen scavenger, acetaldehyde reducing agent, catalystdeactivator, or a combination thereof.
 8. The process of claim 3 whereinan acetaldehyde reducing agent is not present in the polymer meltstream.
 9. The process of claim 1 wherein the modifying polymercomprises a condensation polymer.
 10. The process of claim 9 wherein themodifying polymer is a polyamide, polycarbonate, or polyester.
 11. Theprocess of claim 10 wherein the polyamide modifying polymer isintroduced into the slipstream at a rate sufficient to incorporate 0.1weight % to 10 weight % polyamide in the discharge polymer melt stream.12. The process of claim 10 wherein the polycarbonate modifying polymeris introduced into the slipstream at a rate sufficient to incorporate0.1 weight % to 50 weight % polycarbonate in the discharge polymer meltstream.
 13. The process of claim 9 wherein the modifying polymer is acopolyester.
 14. The process of claim 13 wherein the copolyestermodifying polymer comprises 0.1-100 mole % carboxylic acid modifyingresidues or 0.1 to 100 mole % glycol modifying residues.
 15. The processof claim 14 wherein the carboxylic acid modifying residues comprisesaromatic dicarboxylic acids having 8 to 14 carbon atoms, aliphaticdicarboxylic acids having 4 to 12 carbon atoms, or cycloaliphaticdicarboxylic acids having 8 to 12 carbon atoms.
 16. The process of claim14 wherein the carboxylic acid modifying residues comprises phthalicacid, isophthalic acid, naphthalene-2,6-dicarboxylic acid,cyclohexane-1,4-dicarboxylic acid, cyclohexanediacetic acid,diphenyl-4,4′-dicarboxylic acid, succinic acid, glutaric acid, adipicacid, azelaic acid, sebacic acid, and the like, with isophthalic acid,naphthalene-2,6-dicarboxylic acid, and cyclohexane-1,4-dicarboxylic acid17. The process of claim 14 wherein the carboxylic acid modifyingresidues comprise phthalic acid, isophthalic acid,naphthalene-2,6-dicarboxylic acid, cyclohexane-1,4-dicarboxylic acid,cyclohexanediacetic acid, diphenyl-4,4′-dicarboxylic acid, succinicacid, glutaric acid, adipic acid, azelaic acid, sebacic acid.
 18. Theprocess of claim 14 wherein the carboxylic acid modifying residuescomprise isophthalic acid, naphthalene-2,6-dicarboxylic acid, andcyclohexane-1,4-dicarboxylic acid
 19. The process of claim 14 whereinthe glycol modifying residues comprise cycloaliphatic diols having 6 to20 carbon atoms and aliphatic diols having 3 to 20 carbon atoms.
 20. Theprocess of claim 14 wherein the glycol modifying residues comprisediethylene glycol; triethylene glycol; 1,4-cyclohexanedimethanol;propane-1,3-diol; butane-1,4-diol; pentane-1,5-diol; hexane-1,6-diol;3-methylpentanediol-(2,4); 2-methylpentanediol-(1,4);2,2,4-trimethylpentane-diol-(1,3); 2,5-ethylhexanediol-(1,3);2,2-diethyl propane-diol-(1,3); hexanediol-(1,3);1,4-di-(hydroxyethoxy)-benzene; 2,2-bis-(4-hydroxycyclohexyl)-propane;2,4-dihydroxy-1,1,3,3-tetramethyl-cyclobutane;2,2-bis-(3-hydroxyethoxyphenyl)-propane; and2,2-bis-(4-hydroxypropoxyphenyl)-propane.
 21. The process of claim 14wherein the glycol modifying residues comprise1,4-cyclohexanedimethanol; 2,2,4,4-tetramethyl-1,3-cyclobutanediolunits, and diethylene glycol.
 22. The process of claims 14 wherein thecompositional modifier exhibits an intrinsic viscosity greater than0.45, measured at 25° C. in a solvent consisting of 60 weight percentphenol and 40 weight percent tetrachloroethane.
 23. The process of claim1 wherein a control valve 106 regulates the flow rate of polymer meltpassing through the slip stream.
 24. The process of claim 1 wherein amelt pump is incorporated into the slip stream to regulate the flow rateof polymer melt passing through the slip stream.
 25. The process ofclaim 1 wherein a flow meter is incorporated into the slip stream toregulate the flow rate of polymer melt passing through the slip stream.26. The process of claim 1 wherein the slipstream flow rate can varyfrom 2% to 50% of the discharge polymer melt stream production rate. 27.The process of claim 1 wherein the melt temperature of the slipstream isadjusted to prevent the It.V of the slipstream from degrading by morethan 0.2 dL/g.
 28. The process of claim 1 wherein the melt temperatureof the slipstream is set to within 10° C. of the modifying polymer. 29.The process of claim 1 wherein the melt temperature of the modifiercontaining slipstream is set or adjusted to a temperature differentialno greater than 10° C. relative to the temperature of the continuouslydischarging polymer melt exiting the polymerization reaction.
 30. Theprocess of claim 1 wherein the compositional modifier is introduced intoan extruder, melted, and then pumped into the slip stream to produce amodifier containing slip stream.
 31. The process of claim 1 wherein boththe compositional modifier polymer and the polymer melt from the slipstream are introduced into an extruder located in-line with theslipstream and melt blended.
 32. The process of claim 1 wherein thecompositional modifier is supplied as a continuous flow of polymer meltfrom a second polymerization reactor and is injected directly into thepolymer melt of the slip stream using a melt pump or in-line extruder.33. The process of claim 1 wherein an additive is fed into the extruderwith the modifying polymer and introduced to the slip stream.
 34. Theprocess of claim 1 wherein the additive is fed into the extruder as amasterbatch with the modifying polymer and introduced to the slipstream.
 35. The process of claim 1 wherein the additive masterbatch ismelted and pumped into the slip stream.
 36. The process of claim 34wherein the additive masterbatch comprises a polyester carrier resinhaving an It. V. of at least 0.6 dL/g.
 37. The process of claim 1wherein the additive can optionally be injected into the slip streamusing a pump, either as a liquid or slurry.
 38. The process of claim 1wherein the additive is injected into the slip stream prior tointroduction of the compositional modifier.
 39. The process of claim 1wherein the additive is injected into the slip stream subsequent tointroduction of the compositional modifier.
 40. The process of claim 1wherein a first additive is fed into the slipstream at a first additionpoint and a second additive is fed into the slipstream downstream of thefirst addition point.
 41. The process of any of claims 33-40 whereinsaid additive comprises a UV absorber, reheat rate enhancer, oxygenscavenger, acetaldehyde reducing agent, catalyst deactivator, or acombination thereof.
 42. The process of claim 1 wherein a post-consumerrecycle polyester polymer is added to the continuously produced polymermelt.
 43. The process of claim 1, comprising a static mixer in-line withthe slip stream subsequent to the point where the compositional modifieris added to the slipstream.
 44. The process of claim 1, comprising astatic mixer in-line with the slip stream subsequent to the point wherea first additive is added to the slip stream.
 45. The process of claim Iwherein optionally a melt pump is incorporated at the slip stream exitto provide pressure and control throughput flow rate.
 46. The process ofclaim 1 wherein the metallurgy of the piping, mixers, valves, and pumpscomprising the slipstream are Hastelloy or titanium.
 47. The process ofclaim 1 wherein the modifier containing slipstream is fed into thepolycondensation reactor at a location upstream from the feed locationforming the slipstream.
 48. The process of claim 1 wherein the modifiercontaining slipstream is fed to a location between the final reactor andthe take off point for forming a slipstream.
 49. The process of claim 1,wherein the modifier containing slipstream is fed to a point within afinal reactor for polycondensation and before solidification of thepolymer melt.
 50. The process of claim 1 wherein the modifier containingslipstream is fed into one of the polycondensation finishing reactorswithin final reactor series or into a reactor pipe connecting thepolycondensation finishing reactors upstream of the final reactor. 51.The process of claim 1 wherein the modifier containing slipstream is fedto a point after at least 85% of the time for polycondensing the polymermelt.
 52. The process of claim 1 wherein the modifier containingslipstream is fed to the polyester melt stream after the It.V. of thepolyester melt is within ±0.1 dL/g of the highest It.V. obtained priorto solidification.
 53. The process of claim 1 wherein the modifiercontaining slipstream is fed into the reactor at a point within 20minutes or less prior to solidifying the polycondensed polymer melt. 54.An article obtained by feeding the modified polymer of claim 1 to a meltprocessing zone of an extruder and forming an article from the polymermelt, wherein said melt has an It.V. of at least 0.72 dL/g.
 55. Anarticle obtained by feeding pellets of modified polymer produced by theprocess of claim 1 to a melt processing zone of an extruder, melting thepellets to form a polymer melt, and forming an article from themodified, wherein said pellets have an It.V. of at least 0.72 dL/g. 56.The process in which a static mixer is installed before or after theslipstream is removed in the continuously discharged polymer meltstream.